Bi- and Tricyclic Penta- and Hexacoordinated Phosphoranes with Varying Ring Sizes: Synthesis, Structures, and Reactivity

New tricyclic hexacoordinated phosphoranes 1−6 with
internal N→P coordination containing ring sizes
varying from five to eight membered have been synthesized by oxidative
addition of a quinone or a diol to a cyclic
phosphite. The bicyclic phosphorane
(NC9H6O)P(O2(3,5-t-Bu)2C6H2)((O-2,4-(t-Bu)2C6H2)2CH2)·1/2H2O
(7·1/2H2O)
has been synthesized by adding the
3,5-di-tert-butyl-o-benzoquinone to the cyclic phosphite.
The compound
(NC9H6O)P(2,2‘-OC6H4C6H4O)2
(6) results from a novel ring exchange reaction of a
phosphorinane by a phosphepin
in two ways:  (a) by treating
(OCH2CMe2CH2O)P((OC9H6N)
with 2,2‘-biphenol/N-chlorodiisopropylamine and
(b)
by treating
(Et2N)P(OCH2CMe2CH2O)(2,2‘-OC6H4C6H4O)
with 8-hydroxyquinoline. Treatment of the aminophosphorane
(Et2N)P(OCH2CMe2CH2O)(O2C14H8)
with 2,4,6-trimethylbenzoic acid led to the unique ester
(OCH2CMe2CH2O)P(O){OC14H8O(C(O)-2,4,6-Me3C6H2)}
(10). 31P NMR data for the new compounds
are discussed with respect
to the differing ring sizes and coordination number on phosphorus.
X-ray analysis shows hexacoordination in 2,
4,
and 6 with an N→P bond and pentacoordination in
7 without an N→P bond. The coordinating nitrogen is
trans to
an oxygen of the six-membered ring in 2 and of the
seven-membered ring in 4. The eight-membered ring in
7 spans
a diequatorial position in a trigonal bipyramidal
arrangement.